In general automatic dishwashing detergent powders contain water soluble builder salt, water-soluble silicate, bleach, preferably a water-soluble chlorine bleaching agent, and water-soluble detergent which is usually an organic, low-foaming (i.e. low "sudsing") non-ionic. For best cleaning efficiency and anti-corrosion effects, the compositions are usually formulated with alkaline salts (i.e. sodium and potassium). In the normal environment in the dishwashing machine, the automatic dishwashing compositions generally yield a pH in the range of about 9.0 to 12.0 and more generally about 9.5 to 11.5. The alkaline builder salts which have been used are both of the inorganic type (e.g. pyrophosphates; carbonates, silicates and so forth) and of the organic type e.g. aminocarboxylates such as trisodium nitrilotriacetate, tetrasodium ethylene diamine tetra-acetate, sodium citrate, sodium itaconate, sodium polymaleate, sodium inter polymaleates, such as maleic-acrylic (or vinyl) interpolymers, sodium oxydisuccinate and so forth.
The builder generally functions to increase the cleaning action of the composition by supplying alkalinity and also by removing (i.e. "sequestering") ions which affect the action and efficiency of the organic detergent.
The silicates which have been used are those wherein the Na.sub.2 O:SiO.sub.2 ratio varies from 2:1 to 1:4 and more generally from about 1:1 to about 1:3.4, typically 1:1, 1:2 and 1:2.4.
The bleach employed is generally a chlorine-yielding agent and has been used in varying amounts but generally to give available chlorine levels of from about 0.3% to about 10% and, more often, levels of about 1% to 5%. Typical bleaches are the inorganic types such as sodium, lithium and calcium hypochlorite, and chlorinated trisodium phosphate, as well as the organic forms such as the di- and tri- chlorocyanuric acids and their alkali (e.g. sodium and potassium) metal salts, N-chloracetyl urea, 1,3-dichloro-5,5-dimethylhydantoin, etc.
The nonionic detergents in common usage have been any of the conventional hydrophobe moieties (e.g. C.sub.8 to C.sub.20 alcohols, phenols, amides, acids, etc.) reacted with ethylene oxide (or mixtures with other oxyalkylating agents such as propylene oxide or butylene oxide). Typical nonionics used have been n-dodecanol with 10 moles of ethylene oxide; tetradecyl alcohol-hexadecyl alcohol (1:1 weight ratio) with 5, 10, 15 or 20 moles of ethylene oxide; polyoxypropylenes condensed (i.e. terminated) with oxyethylene groups and having the general formula HO(C.sub.2 H.sub.4 O).sub.x (C.sub.3 H.sub.6 O).sub.y (C.sub.2 H.sub.4 O).sub.z H wherein y=5 to 100 and typically 10 or 15 and x & z may be from about 5 to several hundred e.g. 10, 20, 40, 50, etc. Among the latter type of nonionics have been those where the oxyethylene component comprises from about 15% to 90% on a weight basis of the non-ionic. Types of non-ionic detergent disclosed as generally useful in automatic dishwashing compositions can be found in U.S. Pat. Nos. 3,314,891, 3,359,207, 2,677,700, 2,979,528, 3,036,118, 3,382,176, 4,115,308 and 4,411,810. It has been known and generally described that non-ionic surfactants even though a preferred class of detergents because of their low-foam characteristics, are not, generally, considered "bleach-stable" detergents and where the latter is of importance use of anionic surfactant, albeit higher foamers, has been reported. Illustrative and a discussion of this problem can be found in U.S. Pat. Nos. 4,116,849, 4,005,027 and 4,235,732.
Automatic dishwashing detergents have been provided in two basic forms, as powders and as "liquids" (or semi-liquids or pastes). The powders represent the "first generation". They are simple to formulate, easy to dispense from machines which have, in the main, been designed to handle powders and not liquids; and because of the presence of the formulation "actives" in solid state, (and usually the components comprise separate and discrete particles), there is a minimum of interaction among the composition ingredients. "Liquids," the so-called "second generation" of products in this area, on the other hand, are more convenient to dispense from the package; also they are generally more soluble in water and therefore have less tendency to remain and/or leave residues in the machine dispenser cup. Phase separation leading to decreased homogeneity and an exacerbation of component interaction are among some of the minuses of the liquid system. Some of the U.S. Patents mentioned earlier are specifically directed to "liquid" systems.